Re: [Qemu-devel] [PATCH v4 0/9] enable numa configuration before machine_init() from QMP

[Igor Mammedov <imammedo@redhat.com>]

On Thu, 26 Apr 2018 09:55:40 -0500
Eric Blake <eblake@redhat.com> wrote:

> On 04/26/2018 09:39 AM, Igor Mammedov wrote:
> 
> >>> I'll try to come up with a text for qemu-doc.texi, not about
> >>> deprecating -S but about when --preconfig should be used vs -S
> >>> and where to get list of commands that could be used at preconfig state.    
> >>
> >> Sounds good to me.  Thanks!  
> > how about something like this:
> > 
> > diff --git a/qemu-tech.texi b/qemu-tech.texi
> > index 52a56ae..6951258 100644
> > --- a/qemu-tech.texi
> > +++ b/qemu-tech.texi
> > @@ -5,6 +5,7 @@
> >  * CPU emulation::
> >  * Translator Internals::
> >  * QEMU compared to other emulators::
> > +* Managed start up options::
> >  * Bibliography::
> >  @end menu
> >  
> > @@ -314,6 +315,44 @@ VirtualBox [9], Xen [10] and KVM [11] are based on QEMU. QEMU-SystemC
> >  [12] uses QEMU to simulate a system where some hardware devices are
> >  developed in SystemC.
> >  
> > +@node Managed start up options
> > +@section Managed start up options
> > +
> > +In system mode emulation, it's possible to create VM in paused state using
> > +-S command line option. In this state the machine is completely initialized
> > +according to command line options and ready to execute VM code but VCPU threads
> > +are not executing any code. VM state in this paused state depends on way QEMU
> > +was started. It could be in:
> > +@table @asis
> > +@item initial state (after reset/power on state)
> > +@item with direct kernel loading initial state could be ammended to execute  
> 
> s/ammended/amended/
> 
> > +code loaded by QEMU in VM's RAM and with incomming migration  
> 
> s/incomming/incoming/
> 
> > +@item with incomming migrartion, initial state will by ammended by the migrated  
> 
> and again, for both words
> s/migrartion/migration/
> 
> > +machine state after migration completes.
> > +@end table
> > +
> > +This paused state is typically used by users to query machine state and/or
> > +additionally configure machine (hotplug devices) in runtime before allowing
> > +VM code to run.
> > +
> > +However at -S pause point it's impossible to configure options that affect
> > +initial VM creation (like: -smp/-m/-numa ...) or cold plug devices. That's
> > +when -preconfig command line option should be used. It allows to pause  
> 
> s/to pause/pausing/
> 
> > +QEMU before initial VM creation in preconfig state, query being created
> > +VM at runtime and configure start up options depending on previous query  
> 
> Reads awkwardly.  Maybe:
> 
> It allows pausing QEMU before the initial VM creation, in a new
> preconfig state, where additional queries and configuration can be
> performed via QMP before moving on to the resulting configuration startup.
> 
> > +results. In preconfig state QEMU allows to configure VM only via QMP monitor
> > +with a limited command set which doesn't depend on completely initialized
> > +machine, which includes but not limited to:  
> 
> In the preconfig state, QEMU only allows a limited set of commands over
> the QMP monitor, where the commands do not depend on an initialized
> machine, including but not limited to:

thanks for review,
I amended patches as you suggested.
I plan to respin v6 today with these changes since exit-preconfig
affected several patches in series.

> 
> > +@table @asis
> > +@item qmp_capabilities
> > +@item query-qmp-schema
> > +@item query-commands
> > +@item query-status
> > +@end table
> > +The full list of commands is in QMP schema which could be queried with
> > +query-qmp-schema, where commands supported at preconfig state have option
> > +'allowed-in-preconfig' set to true.
> > +
> >  @node Bibliography
> >  @section Bibliography
> >   
> 
> >> A separate command would have less room for ambiguity.  
> > I've added following instead of reusing 'cont':
> > 
> > ##                                                                               
> > # @exit-preconfig:                                                                 
> 
> This should definitely be mentioned in the docs section of commands
> permitted during preconfig.
done

> 
> > #                                                                                
> > # Exit from "preconfig" state                                                    
> > #                                                                                
> > # Since 2.13                                                                     
> > #                                                                                
> > # Returns: nothing                                                               
> > #                                                                                
> > # Notes: Command makes QEMU exit from preconfig state and proceeds with          
> > # VM initialization using configuration data provided on command line            
> > # and via QMP monitor at preconfig state. Command is available only at           
> > # preconfig state (i.e. if --preconfig command line option).                     
> > #                                                                                
> > # Example:                                                                       
> > #                                                                                
> > # -> { "execute": "exit-preconfig" }                                             
> > # <- { "return": {} }                                                            
> > #                                                                                
> > ##                                                                               
> > { 'command': 'exit-preconfig', 'allowed-in-preconfig': true } 
> > 
> >   
>